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Full text of "Text Book Of Mechanical Engineering"

Piston Rod and Piston.                       247

concave feed (mentioned in Chap. V.), and the flat portion with
horizontal feed. Take again to marking table, block level, as at
H, and scribe both fork and slot-hole, measuring from shoulder.
Drill and slot the fork, and slot-drill the cotter hole. Finally, slot
out the key way to suit the gudgeon; prepare a cotter, and take
out the taper in the hole with round file; then draw-file and
polish. (See Appendix /.,/. 752.)

XXIII.    Piston Rod (Fig.  255).—Centre on V blocks,
and set in the lathe.    Then traverse all over the work to the
diameter at c.    Mark off the various lengths a, b, c, d, and put a
centre pop at each place.    Turn down d to the larger diameter,
f                   and take down the taper at b and d by setting the slide rest, as at

E (Fig. 254). and it should be noticed that if the rest be placed
at the same angle both for rod and hole, the one is bound to
accurately fit within the other. Turn down at a to screwing size,
and chase ; then finish and polish the whole.

The Nut may be turned, bored, and screwed in a chuck, and
the hexagon milled. Lastly, the rod is fitted into the crosshead,
and the cotter hole marked through to the latter, then slot-drilled,
and finished with file.

I                       XXIV.    Piston (Fig. 256).—This is to be turned on the

f<                    rim, and bored to fit the piston rod.   The latter operation is clone

|                   at B, and the former upon a taper mandrel at c, the grooves being

turned at the same time to exact gauge, so as to fit the rings as
^                    truly as is consistent with freedom.    The plug holes, ^, left during

casting (see B, p. 30) are to be drilled and tapped, centres unim-
portant, the plugs being made from a round bar, screwed in the
;                    lathe and parted off to length.    They may be an easy fit in the

I                   holes, but must be painted with sal-ammoniac, so as to form a

rust joint.

The rings are rolled from J-inch brass bar, being received at

/                   the works ready formed, sprung out to a somewhat larger diameter

I                    than the cylinder.    The joint is shewn at a (Fig. 256), and should

1                   be as nearly as possible closed when the piston is in place.

j                         XXV.    Radius Link (Fig. 257).—The forging should be

I                    fairly to shape, being made to template.    First line to thickness,

»                    and plane.    Make a template exactly to drawing A, with the ex-

?;                    ception of the holes, which consist of quarter circles, as at B, with